1. Field of the invention
The invention relates to frame rate up-conversion (FRUC), particularly to an apparatus and method of frame rate up-conversion with dynamic quality control.
2. Description of the Related Art
Frame rate up-conversion (FRUC) is the conversion process between any two display formats with different frame rates. FRUC has various applications, e.g., saving bandwidth in low bit-rate video transmission, reducing movies juddering in converting a 24 fps video source into a higher frame rate and reducing blurring effect in a hold-type liquid crystal display (LCD).
Most FRUC use motion estimation (ME) to obtain motion vectors of moving objects and then perform motion compensated interpolation (MCI) to interpolate images of the moving objects in different frames. Most ME methods calculate motion vectors with the minimum sums of absolute difference (SAD) according to block matching estimation algorithm. However, under certain circumstances, many ME methods are inclined to fall in the trap of the local minimum SAD value. That is, a motion vector with the local minimum SAD value is not necessarily the real motion vector of a moving object; furthermore, even a motion vector with the global minimum SAD value is not necessarily the real motion vector of the moving object.
For example, movie films typically operate at 24 frames per second (fps) while televisions usually use higher frame rate (e.g., 60/120 Hz for NTSC and 50/100 Hz for PAL). FRUC is used to convert a 24 fps film to a higher frame rate for advanced displace devices. According to FRUC, artificial frames are interpolated between two original consecutive frames. FRUC is proposed to obtain better image quality. However, wrong motion vectors degrade image quality significantly and current ME algorithms cannot ensure to find out the correct motion vectors.